When carrying out the seismic design of the bridge, how to choose the appropriate seismic system according to the characteristics of the bridge?

Two Vibration isolation design(Chapter 10 of the "Public Bridge Seismic Regulations") 

It is a passive and negative seismic countermeasure to resist earthquakes by using the structure's own seismic properties (strength, stiffness, ductility). However, control devices (systems) are applied to the structure, and the control devices and structures are jointly subjected to seismic action to tune and mitigate the seismic response of the structure. It is a proactive earthquake countermeasure. The shock isolation design belongs to the latter.

Ductile design - deformation mainly occurs in the substructure, passive and negative seismic countermeasures

Seismic isolation design - deformation mainly occurs in seismic isolation bearings, proactive seismic countermeasures

Vibration isolation design is a general term for shock absorption and isolation, which is a method of vibration control. It is to use the seismic isolation device to extend the natural vibration period of the structure and increase the damping to achieve the purpose of consuming seismic energy and reducing the internal force response of the structure under the premise of meeting the requirements of normal use functions, but the displacement response will increase. 

Bridges that meet one of the following conditions can adopt seismic isolation design:

1) The piers are rigid piers, and the basic cycle of the bridge is relatively short. 

2) When the height of the pier is largely different. 

3) The expected ground motion characteristics of the bridge engineering site are relatively clear, and the main energy is concentrated in the high frequency band.

In one of the following situations, it is not appropriate to use the vibration isolation design: 

1) Under the action of earthquakes, the site may fail. 

2) The stiffness of the substructure is small, and the basic cycle of the bridge is relatively long. 

3) Located in a weak field, the extended period cannot avoid the concentrated frequency band of seismic wave energy. 

4) Negative reaction force may occur in the bearing.

Commonly used shock isolation devices are divided into two categories: integral type and separate type:

Commonly used integral shock isolation devices are:

1) Lead core rubber bearing.

2) High damping rubber bearing.

3 ）Friction pendulum damping isolation bearing

Commonly used separation shock isolation devices are: 

1) Rubber bearing + metal damper. 

2) Rubber bearing + friction damper.

Viscous damper In general, the resilience model of elastoplastic and friction isolation bearings can be bilinear model.